This invention relates to the selective reduction of the contrast of a photograph or other photo-recorded image.
The invention provides camera apparatus and methods which can reduce the contrast with which an image is recorded, which can automatically select the amount of contrast reduction, and which can selectively decrease contrast jointly or separately for different spectral regions, i.e. for different colors being recorded.
Photographic technology has heretofore provided film with various speeds and color sensitivities, and has provided cameras with automatic focus, automatic illumination, and automatic exposure. But control over contrast, which determines the extent to which the photograph captures the tonal character of the scene, has not been attained in a manner suitable for wide commercial application.
Yet reduction of contrast is often desired. For example, it can improve the range of tones recorded from a bright scene, which too often is photographed with harsh highlights and/or underexposed shadows. A reduction in contrast has also long been desired in photographic copiers. The copying of a photograph, whether a positive or a negative, with standard films and standard photo-processing, produces a copy with more contrast, and correspondingly less range of tonal definition, than is present in the original document being copied. Resort to special low contrast films and/or special processing has been a costly and often inconvenient solution.
The prior art of techniques related to this invention for reducing the contrast of a photo-record includes U.S. Pat. No. 3,973,954 of Bean, and No. 3,973,953 of Montgomery. These patents disclose exposing an optically sensitive surface through a lenticular screen in a manner to record an imperfect image. The patents appear to teach that a camera or other optical recording system that provides greater contrast range can be obtained, but at the expense of resolution. U.S. Pat. Nos. 3,973,958 and 3,973,957 also disclose exposure through lenticular screens, but to project sharply focused images for the purpose of increasing sensitivity and speed in a deformation imaging system. Another prior art instant of exposure through a lenticular grating appears in U.S. Pat. No. 3,954,334, where a motor element moves a lenticular screen transversely of image light being recorded.
The 1911 Berthon U.S. Pat. No. 992,151 discloses introducing a refractive surface formed by minute proturbances of microscopic proportions in front of a photosensitive layer, apparently for the purpose of recording different colors. The 1931 U.S. Pat. No. 1,838,173 of Chretien discloses the increase in photographic luminosity by configuring small refracting lenses on a photographic negative such that each lens concentrates exposure to a small area of the negative. The prior art also includes U.S. Pat. No. 2,992,103, which discloses a multi-layer photographic film structure that includes a lenticular screen member through which the photosensitive layers are exposed and through which the resultant recorded image is viewed.
Prior teachings regarding half-tone reproductions also include techniques for selecting contrast. See for example Yule U.S. Pat. Nos. 2,304,988; 2,316,644; 2,407,211; 2,455,849 and 2,691,586; in addition to Denner U.S. Pat. No. 3,506,350, which concerns a print copier.
An object of this invention is to provide a camera method and apparatus for obtaining improved reduction of contrast in a photo-record. A further object is to provide camera method and apparatus which allows control of the contrast reduction.
It is also an object to provide camera apparatus and method which automatically changes the contrast reduction in response to relative brightness range in the scene being recorded.
Another object is to provide a photo-recording method and apparatus for selectively modifying the contrast in highlight, or high exposure, portions of a scene. It is also an object to provide such contrast control separately for different colors.
More specific objects of the invention include the provision of a photographic camera which provides selective controlled reduction of contrast, and the provision of a print copier which can provide a photocopy with the same or lesser contrast than in the original without the use of special films or processing.
It is also an object of the invention to provide a novel film structure for use in photography with reduced contrast.
Other objects of the invention will in part be obvious and will in part appear hereinafter.
The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and apparatus embodying features of construction, combinations of elements and arrangements of parts adapted to affect such steps, all as exemplified in the following detailed disclosure, and the claims indicate the scope of the invention.